Adsorption apparatus comprising a heat recovery system

ABSTRACT

An adsorption apparatus having at least a first and second adsorber unit, each of which is connected to a feed line and return line. Each adsorber unit operates alternately in a desorption phase as a desorber wherein heat is dissipated from the heat transfer medium to the desorber, and in an adsorption phase as an adsorber wherein heat is dissipated from the adsorber to the medium. A heating circuit having a heat source for heating the heat transfer medium and a cooling circuit having a heat sink for cooling the medium are provided. A control unit alternately switches the feed and return lines individually between the heating circuit and the cooling circuit in such a way that the return line with the highest temperature supplies heat transfer medium to the heating circuit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to and claims the benefit under 35 U.S.C.§119 and 35 U.S.C. §365 of International Application No.PCT/EP2006/011666, filed Dec. 5, 2006, and is a continuation of U.S.application Ser. No. 11/996,330, filed Dec. 16, 2008, the disclosures ofwhich are expressly incorporated herein by reference.

BACKGROUND

The subject matter of the present invention is an adsorption machine, inparticular an adsorption cooling machine for refrigeration.

Thermally driven adsorption machines on the basis of solid adsorptionfor heating and cooling purposes have been known for some time. In theprocess conventional working substance pairs—sorption material andadsorbate—such as for example zeolite and water are used. Adsorptionmachines with such a working substance pair are for example described inDE 198 34 696, DE 199 61 629, DE 100 38 636, DE 101 59 652 or DE 102 17443.

Various technical demands are made on adsorption machines. Particularlyimportant are the demands for a high thermal ratio, a high power densityand an easy adjustability of the heat loss. The thermal ratio of theeffective heat to the driving heat—here and in the following namedCoefficient of Performance (COP)—depends essentially on the shares ofthe sorptive and of the sensitive heat transformation during anoperating cycle. By sorptive transformation one understands the releaseof the sorption heat arising in the case of the adsorption of theworking gas or the absorption of the sorption heat required fordesorption, whereas the sensitive heat transformation describes theenergy turnover which occurs in the case of the heating up or coolingdown of the entire system.

In order to achieve particularly high thermal ratios more and moresophisticated systems were developed, wherein in particular through thearrangement of a multitude of adsorber units, which are permeatedsuccessively by the heat transfer medium and switched in a multitude ofcycles, the highest possible heat recovery is strived for. By heatrecovery one understands any recovery of heat—sorptive as well assensitive—from the adsorption phase, wherein the recovered heat can beused for the desorption phase, in order hence to reduce the energyexpenditure of external heat sources for the desorption.

Adsorption machines with two adsorber units are conventionally used forrefrigeration. In these refrigerating machines the adsorber units workalternately as adsorbers or desorbers. The conventional control systemsin the process work between the adsorption phases with heat recoveryphases which partially conduct the heat energy of the adsorber unit thatis still hot to the adsorber unit that is still cold. Through these heatrecovery phases the energy present in the system is reused to a certainextent, so that less energy must be supplied from the outside. Theefficiency of this heat recovery is thus critical for the efficiency ofthe entire adsorption machine.

Conventional control system concepts conduct the heat transfer mediumduring the heat recovery phase in parallel or serial fashion throughboth adsorbers. For this purpose additional components are required, forexample reversing valves or pumps in the heat transfer medium circuitsystem. Moreover this heat transfer medium circuit is operated uncoupledfrom the other circuits. This leads to the pumps mostly connectedexternally to the adsorption machine not being able to send anyvolumetric flow through the system during the time of the heat recoveryand must either be switched off or conducted past the system in abypass. The disadvantages of these systems are the considerabletechnical expenditure, the susceptibility to failure and the highmanufacturing and maintenance costs.

SUMMARY

The invention is based on the object of specifying an adsorption machineand a method for heat recovery in an adsorption machine which areimproved with regard to the named disadvantages. In particular thenumber of components should be reduced in comparison with the knownadsorption machines without worsening the heat recovery, but ratherpossibly improving said heat recovery. In particular the heat recoveryshould be able to be performed without interruption of externallyapplied volumetric flows.

The adsorption machine according to the invention comprises in otherwords at least a first and a second adsorber unit, a heat transfermedium and at least two heat transfer medium circuits with a temperaturedifference ΔT_(X), of which one heat transfer medium circuit is aheating circuit and the other heat transfer medium circuit is a coolingcircuit. Each adsorber unit works in a first desorption phase as adesorber and works in a second adsorption phase as an adsorber, whereinthe heat transfer medium exhibits a lower temperature in a return motionfrom a desorber than in a forward motion to the desorber, and the heattransfer medium exhibits a higher temperature in a return motion from anadsorber than in a forward motion to the adsorber.

Consequently the heat transfer medium is cooled from a forward motion inan adsorber unit working as a desorber, because heat is transferred fromthe heat transfer medium to the adsorber unit, and the heat transfermedium is heated up from a forward motion in an adsorber unit working asan adsorber, because heat is transferred from the heat transfer mediumto the adsorber unit.

The heating circuit basically serves the purpose of transferring heatfrom a heal source which is connected to the heating circuit to the heattransfer medium so that said heat transfer medium can heat up thedesorber. The cooling circuit basically serves the purpose of removingheat from the heat transfer medium by means of a heat sink so that saidheat transfer medium can cool the adsorber.

The heating circuit can also be described as a high temperature circuit(HT circuit) and the coo ling circuit can be described as a meantemperature circuit (MT circuit). Accordingly by HT source the heatsource of the heating circuit is meant and by MT sink the heat sink ofthe cooling circuit is meant, see FIG. 1.

The temperature difference between the high temperature circuit and themean temperature circuit is presently termed as ΔT_(X), wherein thetemperature T_(H) corresponds to the upper limit of the temperaturedifference ΔT_(X) of the two heat transfer medium circuits. Thetemperature T_(H) is that temperature to which the heat transfer mediumshould be set in the high temperature circuit.

The temperature T_(M) corresponds to the lower limit of the temperaturedifference ΔT_(X) of the two heat transfer medium circuits and thattemperature to which the heat transfer medium should be set in the meantemperature circuit.

Through the embodiment according to the invention an adsorption machinecan be created whose heat recovery is at least as great as in the caseof conventional adsorption machines and which in the process manageswithout the integration of additional components in the machine.

In particular the heat recovery of the adsorption machine according tothe invention can take place as a subprocess integrated in the totalprocess, wherein no volumetric flow interruption occurs. The heatrecovery can take place solely with valves and in particular pumps,which are required for the sorption phases anyway.

In particular in an adsorption machine in accordance with the presentinvention provision is made that the temperature difference ΔT_(X) is atleast 10° C. in particular at least 20° C. and especially preferably atleast 25° C. In the process in particular provision can be made that theheat transfer medium in the high temperature circuit exhibits atemperature T_(H) of at least 70° C. and a maximum of 90° C., and inparticular from 75 to 85° C. In principle the adsorption machineaccording to the invention or the method according to the invention ishowever suitable for any temperature differences and temperature level.

In an alternative embodiment of the invention an adsorption machineaccording to the invention can exhibit three heat transfer mediumcircuits, wherein the high temperature circuit 8 having a heat source 3exhibits a temperature difference ΔT_(X) to a second mean temperaturecircuit 9 having a heat sink 4 and exhibits a temperature ΔT_(Y) to athird lower temperature circuit 10, and wherein the temperaturedifference ΔT_(Y) is greater than the temperature difference ΔT_(X).

With an adsorption machine according to the invention advantageouslyeach adsorber unit is not firmly connected to a heat transfer mediumcircuit or assigned to it as usual, but rather is assigned to a heattransfer medium circuit dependent on its temperature in the returnmotion. This is in particular achieved as a result of the valves notboth being positioned in the same direction in the forward and returnmotion of a component in a control phase, but rather having the positionmade dependent on the adjacent temperature level. In an adsorptionmachine according to the invention the valves can be positioned in theforward motion of both adsorber units at the beginning of the heatrecovery phase in such a way that the “new” desorber receives the heattransfer medium from the high temperature circuit and consequently isheated up. The return motion of this “new” desorber, which is stillcold, however continues to be conducted to the mean temperature circuituntil the temperature level increases significantly, in particular by apreset extent or to a temperature equal to or above the return motion ofthe “old” desorber, which is the “new” adsorber. Similar to this theforward motion of the “new” adsorber is connected to the meantemperature circuit, so that this “new” adsorber is cooled. The returnmotion of the “new” adsorber, which is still hot, however continues tobe connected to the high temperature circuit until the temperature leveldecreases significantly, in particular by a preset extent or to atemperature equal to or below the return motion of the “old” adsorber,which is the “new” desorber.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a hydraulic diagram of an exemplifying embodiment of anadsorption machine according to the invention, and

FIG. 2 shows an alternative embodiment having a third adsorber.

DETAILED DESCRIPTION

As one recognized in FIG. 1, the valves of the forward motion group ( .. . _VL_ . . . ) are differently connected during the heat recovery thanthose of the return motion group ( . . . _RL_ . . . ). One advantage ofthis adsorption machine consists in the fact that a heat recovery cantake place without interruption of the external volumetric flows.

With this during the heat recovery, the heat transfer medium isconducted to the high temperature circuit 8 with a heat source 3 at alltimes with the highest available temperature in the return motion of thesystem. As a result of this, on the one hand the energy Which must beprovided from the outside to the system is minimized and on the otherhand through the embodiment of the adsorption machine it is alsoguaranteed that at all times the heat transfer medium will be conductedto the cooling circuit with the lowest temperature, so that the leastpossible energy must be recooled. In particular, the energy requirementsare reduced when in accordance with an embodiment of the inventionpumps, as they are described in the introductory part of the descriptionwith regard to the known control concepts, are conserved.

In particular an adsorption machine according to the invention comprisestwo adsorber units 1 and 2. This adsorption machine can in particularproduce cold in a two-stage, cyclical process. In order to generate acontinuous cold flow at least two adsorber units are counter connected,so that one adsorber unit is being dried while the other one producescold. Fundamentally this process runs all the more effectively the morethe sorption material has been dried previously—which in turn bestsucceeds with higher driving temperatures.

Accordingly an adsorption refrigerating machine is also the subjectmatter of the present invention. This adsorption refrigerating machinecomprises at least two adsorber units, one heat transfer medium, atleast two heat transfer medium circuits with a temperature differenceΔT_(X) and one control unit, wherein each adsorber unit works in a firstdesorption phase as a desorber and in a second adsorption phase works asan adsorber, and wherein the heat transfer medium in a return motion ofthe desorber exhibits a lower temperature than in the forward motion tothe desorber and wherein the heat transfer medium in a return motion ofthe adsorber exhibits a higher temperature than in a forward motion tothe adsorber, and wherein the heat transfer medium with the highesttemperature in the return motion of the first or any further adsorberunit is connected to the high temperature circuit.

Along with the adsorption machine itself a method for heat recovery inan adsorption machine is also the subject matter of the presentinvention. In especially preferred manner in the process thetemperatures of the return motions are compared with each other and thereturn motion with the highest temperature is assigned to the hightemperature circuit.

The operating cycle of an adsorption machine according to the inventioncan flow as follows. First minerals with a large inner surface, inparticular zeolite or silica gels, are dried by heat supply during adesorption phase. When the material has been sufficiently dried the heatsupply is stopped and a valve to a water container is opened. Due to theenormous inner surface and the special crystal structure there is a verygreat suction of water vapor or the evaporating of water in the secondcontainer. As is the case with any evaporation process there is now agreat temperature decline in the water depending on the operating stateup to the formation of ice.

In order to produce a continuous cold flow two such systems are counterconnected so that one adsorber unit is drying while the other one isproducing cold. Alternately the present adsorption machine can comprisethree adsorber units or at least three adsorber units. In particularprovision is made in the process that one adsorption machine comprises amaximum of five adsorber units. In principle however the output of theadsorber machine can be continuously expanded by the simple addition offurther adsorber units.

With an adsorption machine in accordance with the present invention inparticular by a reduction of the necessary pumps the current consumptionand also the generation of noise can be significantly reduced. At thesame time the electrical efficiency is improved. For example theadsorption machine can exhibit pumps exclusively in the external heattransfer medium circuits, that is between the heat sources and/or heatsinks and the adsorber units, for example a single pump per eternalcircuit, as shown in FIG. 1. The adsorber units themselves can bedesigned free of pumps. A condenser 7 is connected in the high and midtemperature circuits 8 and 9, and an evaporator 6 is connected in thelow temperature circuit 10. FIG. 2 illustrates an alternative embodimentincluding a third adsorber 20.

Waste heat or excess heat from existing systems can be used as a heatsource, for example engine-based cogeneration systems, solar plants orprocess waste heat.

1-20. (canceled)
 21. A method for heat recovery in an adsorption machinecomprising at least a first and a second adsorber unit which are eachconnected to a forward motion (VL) and a return motion (RL), in order tosupply heat from a heat transfer medium of the first adsorber unitconducted through the forward motion (VL) to the second adsorber unit orto remove said heat from the first adsorber unit to the heat transfermedium and further comprising at least two heat transfer mediumcircuits, namely a heating circuit with a heat source for heating up ofthe heat transfer medium, and a cooling circuit with a heat sink forcooling of the heat transfer medium, wherein each adsorber unit worksalternately in a desorption phase as a desorber, wherein heat is removedfrom the heat transfer medium to the desorber and in an adsorption phaseas an adsorber, wherein heat is removed from the adsorber to the heattransfer medium; and the forward motions (VL) and the return motions(RL) are switched individually alternately to the heating circuit andthe cooling circuit in such a way that the return motion with thehighest temperature always feeds its heat transfer medium to the heatingcircuit; characterized in that in the transition of the first adsorberunit from the desorption phase to the adsorption phase and in thetransition of the second adsorber unit from the adsorption phase to thedesorption phase or vice versa, first the forward motion (VL) of thefirst adsorber unit which is connected as the new desorber is connectedto the heating circuit so that the new desorber is fed from the heatingcircuit and thus heated up, and the return motion (RL) of this newdesorber continues to be connected to the cooling circuit until thetemperature level of the heat transfer medium in the return motion (RL)is increased by a preset extent, or is warmer than the return motion(RL) of the second adsorber unit, and the return motion (RL) of thesecond adsorber is connected to the cooling circuit so that this secondadsorber is cooled and the still warm return motion (RL) of the secondadsorber continues to remain connected to the heating circuit until thetemperature of the heat transfer medium in the return motion (RL) hasdecreased by a predetermined extent, or up to or below the temperatureof the return motion (RL) of the ether second adsorber unit.
 22. Themethod in accordance with claim 11, characterized in that the returnmotion (RL) with the lowest temperature is always switched in such a waythat it feeds its heat transfer medium to the cooling circuit.
 23. Themethod in accordance with claim 12, characterized in that the switchingof the forward motions (VL) and of the return motions (RL) takes placeby means of a control unit which compares the temperatures of the returnmotions (RL) with each other.
 24. The method in accordance with claim11, characterized in that the switching of the forward motions (VL) andof the return motions (RL) takes place by means of a control unit whichcompares the temperatures of the return motions (RL) with each other.